The present invention relates to a surgical fastener or device (implant) formed in the shape of a screw and washer system and the method for manufacturing the same. The surgical implant of the present invention is particularly but not solely intended to be used in repair surgery for the tendons of the rotator cuff.
Tearing and degradation of the tendons of the rotator cuff muscles is a common and potentially painful and debilitative problem affecting thousands of people each year. The repair of the rotator cuff nearly always requires that the surgeon affix tendon to bone. Initially, surgical treatment of this condition required open surgery. To reduce the trauma of open surgery, arthroscopic surgical techniques have been developed to treat this condition. In both open and arthroscopic surgery, surgeons presently use sutures to affix torn tendons to the humeral head. Specifically, the surgeon will suture the tendon to the humeral head by drilling holes entirely through the bone and running the sutures through the holes (intraosseous or transosseous suturing). See e.g., Ellman, Gartsman, Arthroscopic Shoulder Surgery and Related Procedures, pp. 178-79, 189-97 (1993); and Iannotti, The Rotator Cuff: Current Concepts and Complex Problems, p. 18-19 (1998), the entire disclosures of each of which are incorporated herein by way of this reference.
The use of sutures can be problematic for several reasons. The surgeon must carefully drill holes entirely through the humeral head. Suturing the tendon to the bone through the drillhole is an intricate and exceedingly time consuming process, particularly when done arthroscopically. Sutures may easily break or tear out of the tissue that is being sutured, rendering the cuff repair a failure. Alternatively, sutures may stretch or otherwise allow portions of the repaired tendon to separate from the humeral head (causing diastasis), which results in poor tendon-to-bone healing. Sutures may also strangulate the tissue being sutured. Also, generally nonabsorbable sutures must be used because absorbable sutures degrade too quickly. These nonabsorbable sutures, however, represent a foreign body that can cause irritation or other post-operative problems in the shoulder joint.
In an attempt to prevent sutures from easily tearing out of a tendon, some surgeons have used small plates to help distribute the force of the sutures across a greater cross section of the tendon, as described, for instance, in EP 520,177, the entire disclosure of which is incorporated herein by way of this reference. Such plates, however, do not address the weakness of sutures generally or the difficulty and time-consuming nature of using sutures. Further, such plates can reduce vascularization of the tendon, resulting in tissue necrosis.
One alternative to intraosseous suturing is the use of a suture anchor in the humerus. The suture anchor is inserted into a hole in the humeral head and the tendon is thereby sutured to bone. However, little study has been done with suture anchors in the repair of rotator cuffs and there is a concern about the pull out strength of suture anchors. This is of particular concern where the humeral head has become osteoporotic. As a result, such suture anchors present a problem in rotator cuff repair surgery. If a suture anchor pulls out, not only is the cuff repair jeopardized, the anchor may cause further additional damage and/or discomfort within the shoulder joint. This procedure also has the aforementioned difficulties concerning the use of suturing in the tendon. Further, if the suture anchor is not made of a bioabsorbable material, then its continued presence in the humerus could lead to post-operative difficulties due to the patient""s possible negative reaction to the foreign material of the anchor or migration of the anchor.
Therefore, it is a goal of the present invention to provide a surgical fastener that is easy and quick to use, thereby reducing the length and difficulty of surgical procedures.
It is further a goal of the present invention to provide a surgical fastener that may, if desired, be used arthroscopically, thereby reducing operative trauma to the patient.
It is further a goal of the present invention to provide a surgical fastener strong enough and configured so as to effectively withstand the strong pull out forces involved with the fixation of rotator cuff tendons, thereby allowing proper healing of rotator cuff tears.
It is further a goal of the present invention to provide a fastener that is designed to firmly hold soft tissue to bone without damaging the soft tissue.
It is further a goal of the present invention to provide a surgical fastener that will biodegrade and is of minimum mass, thereby reducing the risk of post-operative complications due to the presence of the fastener in the patient.
It is further a goal of the present invention to provide a surgical fastener that has a low profile, thereby reducing irritation to the surrounding tissues.
It is further a goal of the present invention to provide a surgical fastener that may be self-tapping, thereby reducing the length and difficulty of surgical procedures.
It is further a goal of the present invention to provide a surgical fastener that exposes a broader surface area of the tendon to bone.
It is further a goal of the present invention to provide a method for manufacturing the surgical fastener having the aforementioned benefits. As can be seen from the following description, these and other goals are achieved through the present invention.
The surgical fastener of the present invention comprises a screw and a washer for attaching soft tissue to bone, such as attaching tendons of the rotator cuff to the humeral head. The screw is specially configured to have relatively tall threads for achieving strong purchase within the humeral head. The shank and head of the screw is relatively narrow, in order to minimize the mass of the screw and damage to the rotator cuff. The tip of the screw may be sharpened to form a trocar (pyramidal) or fluted cutting tip, for ease of insertion.
Surrounding the shaft of the screw of the present invention is a washer. The diameter of the annular opening of the washer through which the shaft of the screw passes is larger than the diameter of the shaft of the screw, yet smaller than the outer diameter of the threads and/or the head of the screw. Thus, the washer can freely slide up and down and rotate around the nonthreaded portion of the shaft, yet cannot be easily removed or otherwise separated from the screw without damaging the screw or the washer. The washer may further comprise relatively long protrusions or spikes on its lower surface. These spikes allow the washer to securely grip the soft tissue and hold it to the bone, yet are long enough so that the vascularity of the soft tissue is not compromised, thereby minimizing necrosis. The washer may also have a recess or indentation on its upper side for receiving the head of the screw so that the screw and washer have a low profile when inserted.
The screw and washer comprise a strong, durable biodegradable material. The material is preferably an oriented, fibrillated polymer/copolymer material, such as those described in U.S. Pat. No. 4,968,317, the entire disclosure of which is incorporated herein by way of this reference.